1. Field Invention
The present invention relates generally to a method and apparatus for charging an energy storage device, such as a battery, in a power supply and, more specifically, to a method and apparatus for simultaneously or sequentially charging an energy storage device and providing electric power to a load with an intermittent and/or variable energy source.
2. Description of the Prior Art
In recent years, the use of alternative energy or power sources such as, for example, solar energy, wind energy, and geothermal energy, has become increasingly important. In addition, the desire to place such alternative energy or power sources in remote locations unreachable by conventional electric power or utility grids has steadily increased. For example, a telephone, radio, oven or other device may be located far from traditional electric power grids or utilities and powered by solar or wind energy.
In a typical configuration of a remotely located device requiring electric power for operation, a power source may be used to charge and/or recharge a battery, capacitor, or other energy storage source. The power source and the battery may be used to supply electric energy to the device either sequentially or simultaneously. For example, a remotely located emergency radio may be connected to a battery to provide power to the radio. A solar panel or other energy source can be connected to the battery to maintain a charge in the battery. Additionally, the solar panel may directly provide power to the radio. The solar panel may be used to provide electric power to the radio during the day as well as charging the battery. During the evening or when the sky is overcast or cloudy such that the solar panel cannot generate enough electric power for the radio, the battery may be used to provide electric power to the radio.
Unfortunately, in many configurations wherein a recharging power source, such as a solar panel or solar array, is used to charge a battery, battery pack, or other rechargeable power source that is, in turn, used to provide power to a device, such as a remotely located radio or telephone, the recharging power or energy source is oversized in order to maintain the battery at or above its rated nominal voltage or energy storage capacity. In addition, the battery is often oversized itself to insure that the battery does not discharge below the minimum required voltage needed to operate the device during, for example, periods of cloudy weather or nighttime operation. As a result, the battery is maintained in a fully charged or overcharged state which reduces the battery's capacity and ability to maintain a charge and leads to a premature failure of the battery. Furthermore, efficiency of power delivery to a load from either the recharging power source or the rechargeable power source is often significantly reduced, thereby wasting power.
Therefore, in spite of the developments in the art in battery charging technology, there remains a need for a charger or charging system for a battery or other power source that is simple to construct, allows for the charging of a battery or other power source simultaneously or concurrently with delivery of electric power to a load, improves battery charging efficiency, improves efficiency of electric power delivery to a load, and does not cause the battery to fail prematurely.